This invention relates to a printing machine which directly prints a character or figure on recording paper in accordance with an electric signal.
There is, heretofore, widely known a so-called ink jet printing machine for ejecting liquid ink to effectuate printing. The recording speed of a ink jet printing machine depends upon the speed at which the recording ink droplet is formed as a character and the relative moving speed of a nozzle for producing the ink droplet with respect to the recording paper.
In the prior art it is generally recognized that the maximum speed for the recording ink droplet to be formed is approximately 1 MHz even by using a charged amount control system of the fastest printing speed in all the systems. The relative moving speed of the nozzle depends upon the structure and configuration of the nozzle. The acceleration of the nozzle is limited due to the mechanism in such a system for reciprocatingly moving the nozzle on a rectilinear line and for moving the recording paper perpendicularly with regard to the nozzle.
Therefore, a so-called a multi-nozzle system has been proposed for disposing a number of nozzles perpendicularly with respect to the feeding direction of the recording paper. The aforementioned charged amount control system uses single nozzles that are aligned in large numbers in a parallel arrangement. This causes the cost of such a system to become expensive.
Since the recording ink droplet flies in the space between the recording paper and a nozzle, high accuracy is required for the disposition of the recording paper at sequential timing with regard to the recording ink droplet formation timing. A printing machine construction is disclosed in Japanese Patent Laid-Open No. 9622/1973 wherein ink is injected as required in accordance with a pressure pulse. It is considered to be a difficult problem to align the perforations of a great number of fine holes at a high density corresponding to the recording density. Furthermore, since the droplets of recording ink must fly across the distance between the recording paper and the injecting nozzle, high precision timing between the formation of the droplets and the instantaneous position of the recording paper is required. This is because, when a character or the like is exhibited as a collection of image elements, a high quality reproduction of the character or the like cannot be obtained unless the ink droplets constituting the image elements are always positioned correctly on the recording paper.
Considering the quality of the prints on the recording paper, since the injecting type printing device in which ink is injected through fine holes, this requires the use of a low viscosity which ink quickly diffuses into the paper tissue upon arrival on the surface. This tends to produce features such as producing low grade printing having much blur and of a low reflection density. Hence, such systems have many disadvantages.
Also, an ink jet printing machine for ejecting a liquid ink has features that allow halftone color to be printed at relatively high speed. However, in order to reproduce natural color, many important difficulties have existed in the printing technology. One of problems resides in the ink. In normal printing process, an ink including a solvent, pigment, etc. is transferred onto a recording paper so that the surface of the ink is dried with a resin layer due to its evaporation or bridge formation among molecules by the exposure of ultraviolet rays for solidification. In color printing, three plates for dots of three primary colors such as cyan, magenta and yellow separated from the original picture are used to print with three primary color inks of cyan, magenta and yellow. Since the ink is ejected from the fine hole in an ink jet printing machine, the ink is easily evaporated and dried which tends to block the ink supply system such as nozzles or the like and tends to evaporate a great deal of solvent resulting in difficulty in usage.